Transportation of cold liquids and safety means

ABSTRACT

919,755. Storing liquefied gases. CONCH INTERNATIONAL METHANE Ltd. July 18, 1961 [Sept.12, 1960], No. 25951/61. Class 8(2). [Also in Groups XXIX and XXXIII]. A system for protection against leakage of cold liquid, e.g. liquefied gas, from a storage tank 10 which is mounted within a thermally insulated space with the side walls of the tank being spaced from the insulation 16, comprises a liquid receiving means adjacent the bottom of the tank extending beyond the side walls of the latter and upwardly into the space 28 about the tank, and means for removing liquid from the liquid receiving means. As described, the tank is housed within the hull 14 of a ship which is lined with the insulation 16, e.g. balsa wood, the tank having an inlet pipe 18, a discharge pipe 24 and a vent pipe 25. The liquid receiving means is in the form of a receptacle 30 having a bottom wall 32 and side walls 34. The receptacle may be of metal, wood or plastic and may be reinforced. The bottom of the tank rests upon beams 38 supported on the bottom wall 32 of the receptacle. Alternatively, the beams 38 may be omitted, the tank resting on the bottom wall 32, or the bottom wall of the tank may be extended beyond the side walls thereof replacing the bottom wall of the receptacle, Fig. 2 (not shown), or the receptacle may be formed by a membrane, e.g. a film of metal or plastics, supported by and fixed to the insulation 16. Keys and keyways may be provided between the tank and the supporting floor 37. One or more drains 40 are provided in the receptacle, leading to a pump 44 which returns liquid collected in the receptacle through a pipe 46 to the tank 10 or to other receivers or to a pipe 47 having its outlet extending rearwardly of the ship. The pump 44 may be automatically started when the cold liquid contacts electrodes 50, 52; alternatively, a thermocouple may be used to start the pump. The side walls of the receptacle may be inclined outwardly towards the insulation 16 and the inner surface of the latter may be covered with a liquid and vapour impervious layer, e.g. a membrane of aluminium. More than one tank may be mounted in the insulated space and the liquid receiving receptacle may be provided for each tank or for each one of groups of the tanks or for all the tanks. The ship may be of double hull construction. Specifications 853,367 and 854,705 are referred to.

NOV. 12, 1963 RADD 3,110,157

TRANSPORTATION OF COLD LIQUIDS AND SAFETY MEANS Filed Sept. 12, 1960 2Sheets-Sheet 2 {KC f; FIG. 2

II V) w HAZHU United States Patent 3,110,157 TRANSPORTATION OE COLDLIQUIDS AND SAFETY MEANS Frederick Radd, Ponca City, Okla., assignor toConch International Methane Limited, Nassau, Bahamas, a

corporation of the Bahamas Filed Sept. 12, 1960, Ser. No. 55,481 4Claims. (Cl. 6249) This invention relates to the ship transportation ofextremely cold liquids in self-suflicient containers of large capacity,and it relates more particularly to a safety feature employed in asystem of the type described for the purpose of maintaining control ofthe extremely cold liquid cargo which might inadvertently or otherwiseescape from the containers, thereby to avoid the extremely dangerousconditions which would otherwise develop.

It is an object of this invention to produce a means for thetransportation in large volume of extremely cold liquid, and it is arelated object to provide safety means employed in combination therewithto protect the ship or other structure from the extreme cold of theliquid in the event of escape of the liquid from the container.

These and other objects and advantages of this invention willhereinafter appear and for purposes of illustration, but not oflimitation, embodiments of the invention are shown in the accompanyingdrawings, in which FIGURE 1 is a schematic sectional elevational view ofa system which may be employed for the safe transportation of anextremely cold liquid,

FIGURE 2 is a sectional elevational view similar to that of FIGURE 1,showing a modification in the safety means, and

FIGURE 3 is a similar sectional elevational view of a corner of astructure embodying a further modification.

This invention can best be illustrated by reference to the over-watertransportationof natural gas in a liquefied state from a source ofplentiful supply to an area where a deficiency exists. It will beunderstood that the concepts described will have similar application toship transportation of other extremely cold liquids in large quantities,such as liquefied air, oxygen, hydrogen, nitrogen, and the like.

Ship transportation of such gas or gases in a liquefied state isdesirable because of the greater volume of gas than can be housed withina storage space since a gas is reduced by circa 600 in volume whenconverted from a gaseous state to a liquid. To make the transportationcommercially feasible, it is desirable to embody means fortransportation of such liquefied gas in large volume. It becomesimpractical to construct tanks or containers of large capacity forhousing such liquids at pressures which greatly exceed atmosphericpressure because otherwise tanks of extremely high strength would berequired, thereby markedly to increase the initial cost in equipment. Asa. result, the practical concepts reduce the practice to thetransportation of liquefied gas in large volumes in containers whereinthe liquefied gas is housed at about atmospheric pressure.

With natural gas, composed mostly of methane, this means thetransportation of the liquid in tanks of large capacity at about theboiling point temperature of the liquefied gas which, for natural gascomposed mostly of methane, may range from -240 to 258 F., dependingupon the amount of higher boiling hydrocarbons that are present.

It is known that the steel plate of which the ships hulls are usuallyconstructed will lose their ductility and will therefore becomeembrittled and lose strength when reduced to a temperature below 100 F.As a result, such steel plate cannot be employed in the construction ofthe liquid storage tanks, and it becomes extremely important 3,110,157Patented Nov. 12, 1963 to embody means within the ships structure toprotect the structural elements of the ship from the cold of the liquid,otherwise the ship will be faced with possible destruction upoiitransmission of cold from the liquid to the ships stee One means whichhas been developed for commercial practice in ship transportation ofliquefied gas is fully described in the co-pending application of Henry,Serial No. 582,965, filed May 7, 1956, and entitled Ship. In accordancewith the teachings thereof, the liquified gas atabout atmosphericpressure is housed within a large tank of polygonal shape and formed ofsuch materials as aluminum or alloys of aluminum, stainless or otherhigh nickel or austenitic steels, copper or alloys of copper and thelike which do not become embrittled at cryogenic temperatures. The tanksare mounted within the hold space of the ship lined with a relativelythick layer of insulating material, as represented by blocks of balsawood or other material having low heat conductivity. The ship ispreferably formed with an outer steel hull and an inner hull in closelyspaced parallel relationship with the outer hull to define a confinedspace therebetween through which water or other fluid may be introducedor circulated for temperature control as well as for ballast.

In a double hull construction of the type described, the insulation isapplied as a lining to the inner surface of the inner hull. Whenadequate protection is available to prevent cold of liquid escaping fromthe tanks from transmission to the ships structure, it becomes possibleto construct the ship without the inner hull. As a result, it will beunderstood that this invention is applicable to ships with or withoutthe double hull construction.

The problem of the control of escaping liquid is complicated by thenecessity to maintain freedom for expansion and contraction movements ofthe tank relative to the structural elements of the ship and the tanksupports, since the tank will be subject to wide dimensional changebetween the time that it is charged with liquefied gas at about -258 F.and the time when the tank is free of liquid cargo such that thetemperature of the walls can rise to as much as plus F. Stabilization toposition the tank while permitting freedom for expansion and contractioncan be achieved by means described in the previously issued patent ofHenry, No. 2,905,352, or by cable means described in the copendingapplication of Joseph F. Stroschein, Serial No. 31,403, filed May 24,1960, and entitled Cold Cargo Transportation Means."

Another problem confronting the protection of the ships structure fromthe cold of the liquid which might escape from the tanks is the shiftingforces and angles normally resulting from the pitching and rollingmovements of the ship during navigation. A ship may roll by as much as40 degrees in either direction in a bad sea, thereby to imposeconsiderable shifting of the loads upon the walls of the tank andthereby also to impose problems with respect to maintenance of theliquids which find their way outside of the tank by reason of leakage,splash, or partial failure of the tank.

Referring now more specifically to the drawings for illustrations of theconcepts of this invention, the metal storage tank is represented by thenumeral 10 and the liquified gas stored therein is represented by thenumeral 12. The tank is illustrated as being housed within an insulatedhull 14 of the ship lined to provide a relatively thick layer 16 of astructurally strong and dimensionally stable insulation, such as balsawood.

The tank is provided with an inlet pipe 18 which extends into the tankthrough the top wall 20 for the introduction of liquid cargo into thetank and which is provided with a fiow control valve 22 for regulatingthe flow of vapors and fiuid therethrough. A discharge pipe 24 extendsdownwardly through the tank to a point adjacent the bottom side for usein, the removal of liquid cargo, and it, too, is provided with a flowcontrol valve 26 for regulating the flow of vapors of fluidstherethrough and a vent pipe 25 extends into the tank into communicationwith the vapor space for release of vapors collecting above the liquidlevel.

In accordance with the concepts of this invention, a space 28 isprovided between the side walls of the tank and the insulation 16disposed outwardly thereof. Each tank is provided with a receptacle 30extending outwardly from the bottom side of the tank, such for example,as the pan'illustrated' in FIGURE 1 shaped to correspond with thecross-section of the tank and dimensioned to have a" length and widthgreater than the corresponding dimensions of the tank to span the bottomwall 32 and extend into the space 28 between the side walls of the tankand the insulation. The side walls 34 of the pan extend upwardly intothe space about the sidewalls of the tank to provide a trough 36 intowhich the liquid cargo escaping from the tank and flowinggravitationally downwardly along the side walls of the tank can collect.While it is sufiicient if the side walls 34 of the receptacle extendupwardly for a short distance beyond the bottom wall of the tank, it ispreferred to dimension the side walls to extend beyond the lower quarterof the tank so as to retain liquid escaping from the tank and flowinggravitationally down the side, notwithstanding the angular movement ofthe ship at angles as great as 40 degrees responsive to the pitching androlling movements of the shi its receptacle should be formed ofmaterials which are impervious to the liquid cargo and insensitive tothe cold of the liquid. For this purpose, the receptacle can befabricated of metal suitable for tank construction, or of wood or ofplastic, with or without reinforcement.

The bottom wall 32 of the receptacle can rest on the floor 37 ofinsulating material, and the bottom wall of the tank can rest upon the.top surface of the bottom wall of the receptacle, or the tank'bot-tomwall can be supported in spaced relationship with the bottom wall of thereceptacle as by means of beams 38 to provide a spaced I relationtherebetween and thereby increase the capacity of the receptacle toretain liquid as illustrated in FIGURE 1. Instead, the receptacle mayconstitute a side wall 34' and a bottom wall 32' dimensioned tocorrespond with the spaced relationship between said side wall 34' andthe tank, and which is secured in sealing relationship to the lower edgeof the tank to provide a receptacle in the form of a trough 36' whichextends all about the lower edge of the tank, with the side wall of thecontainer defining the inner wall of the trough, as illustrated in FIG-URE 2. By way ofstill further modification, use can be made of areceptacle which is not free standing but instead relies upon theinsulation for support. For example, as shown in FIG. 3, use can be madeof a membrane 34 such as a film of metal or plastics fixed to the lowerpart of the insulation surrounding the tank to form a receptacle.

When a key and keyway construction (not shown) is employed .to stabilizethe position of the tank, the bottom wall of the pan can be constructedto provide recessed keyways dimensioned to be received in correspondingkeyways in the supporting floor and into which the keys on the bottomside of the tank are received; or vice versa, the keys may be formed inthe pan and floor for engagement into corresponding keyways provided inthe bottom wall of the tank.

Since leakage occurring in the walls of the tank will usually continueuntil the ship is docked for removal of liquid cargo to enable repair ofthe tanks, it is desirable to provide means for the disposal of theliquid as it collects in the receptacle. In the preferred practice, theliquid collected in the receptacle will be displaced for disposal as bydumping the liquid overboard while the ship is at sea, but it will beunderstood that the liquid collected can be returned to the tanksor toother receivers on the transportation means. For this purpose, one ormore drains 40 are provided in the bottom wall of the receptacle forconnection by pipes 42 to the intake side of a displacement pump 44 bywhich the liquid is forced through a pipe 46 to the filling pipe 18,whereby liquid from the pan is returned to the tank, or to. a pipe 47having itsloutlet preferably extending rearwardly of the ship fordumping the liquid into the sea. When the tank rests upon the topsurface of the pan, or when the receptacle merely constitutes thetrough, it will usually be suflicient to locate the drain or drains inthe base of the trough for communicating the liquid with thedisplacement pump. When the tank is supported in spaced relationshipwith the bottom wall of the pan, as illustrated in FIGURE 1, one or moredrains can be located in intermediate portions of the pan bottom wall,and such drains can be located advantageously in downwardly deformedbasins or sumps for more complete drainage of liquid from the pans forreturn to the tank. V

With such cryogenic liquids, it is preferred to make use of means fordirect displacement of the liquid without drainage or other below deckinstallations thereby to avoid bottom connections. For such purpose, asillustrated in FIGURE 2 use can be made of a deep well pump 60 or a gaslift means or other suitable ejector means for direct displacement ofcollected liquid upwardly through a pipe 62 extending upwardly throughthe space 28 and over the deck for release to the sea or else intocommunication with a pipe extending into the tank if it is desired toconserve the liquid.

It will be apparent that in the event of development of any cracks,breaks, or leaks in any of the walls of the tank, liquid escapingthrough said openings will, for the most part, remain in a liquefiedstate by reason of the extremely cold temperature of the portions of thewall below the liquid level. Such escaping liquid will flow by gravitydown the side walls of the tank into the trough of the receptacle,notwithstandingthe normal angular movements of the ship in navigation.Such liquid will be collected and retained in the receptacle. In theevent that the leakage is of such proportion as to cause substantialamounts of liquid to be collected in the receptacle, such liquid can bereturned immediately to the tank thereby constantly to maintain controlthereof. Since such leakage cannot alwaysbe immediately detected, it isdesirable to provide means for automatically initiating activation ofthe liquid displacement means responsive to the presence of liquid inthe receptacle. For this purpose, sensing means, such as electrodes 50and 52, are provided in the base of the trough for initiating operation.of the displacement pump when the electrodes are contacted with liquid,thereby automatically to recircu-late liquid from the receptacle throughthe return pipe 46 to the always open portion of the supply line 18 forreturn to the tank.

Instead of the liquid level sensing means shown in FIGURE 1, use can bemade of a thermocouple 54 connected by the conductor 56 to thedisplacement pump means to initiate operation thereof in response to thecold of the liquid present in the trough.

It will be obvious to those skilled in the art that the invention iscapable of numerous modifications which will become apparent from theforegoing description. For example, the pump 44 could be mounted -inasuitable area within the insulated space or it could be mounted asubstantial distance from the cargo tank and the insulation surroundingthe tank. The side walls 34 and 34 of the receptacle, illustrated in thedrawings as extending perpendicularly from the bottom wall, can beinclined outwardly towards the insulation to enhance the the innersurface of the insulation can be provided with a suitable liquidandvapor-impervious layer, such as a membrane of aluminum and the like,which would operate to deflect liquid escaping from the tank into thetrough or receptacle, thereby to enhance the control of the fluid flow.

It will be understood that the foregoing represent emergency meansimportant to the safety of the ship transport or to storage handlingsuch extremely cold liquids. The described means will be found to beextremely valuable when partial failure occurs in one or more of thetanks while, the ship is at sea. The means described will operate tomaintain control of the liquid cargo for protection of the ship'sstructure from the cold of the liquid, while also minimizing loss ofliquid until the ship can be docked for removal of the liquid cargo toland storage to enable more permanent repair of the tanks.

It will be understood that more than one tank can be mounted for use inthe insulated space and that the described safety means may be adaptedfor each of the separate tanks or for combinations thereof or for theentire cluster of tanks within the hold space. It will be furtherunderstood that other changes in the details of construction andarrangement may be made without departing from the spirit of theinvention, especially as defined in the following claims.

I claim:

1. A liquid protecting system in the storage and transportation ofextremely cold liquids in self suflicient storage tanks mounted within athermally insulated space with space between the sides of the storagetank and the thermal insulation comprising a liquid receiving meansadjacent the bottom side of the storage tank and dimensioned to extendbeyond the side walls of the tank and upwardly into the space about thetank between the outer wall of the tank and the thermal insulationspaced therefrom and to a height substantially less than the height ofthe tank, and means for removing liquid from said liquid receivingmeans, wherein the cold liquid receiving means comprises a pan-shapedmember having a contour corresponding to the cross-section of the bottomof the storage tank and having side walls extending substantiallyperpendicularly upwardly from the edges of the bottom wall of thepan-shaped member into the space between the side wall of the tank andthe insulation, and in which the pan-shaped member rests on thethermally insulating floor of the insulated space, and means forsupporting the bottom wall of the tank in vertically spaced apartrelation from the bottom wall of the pan.

2. 'A liquid protecting system in the storage and transportation ofextremely cold liquids in storage tanks mounted within a thermallyinsulated space with space between the sides of the storage tank and thethermal insulation comprising a liquid receiving means adjacent thebottom side of the storage tank and dimensioned to extend beyond theside walls of the tank and upwardly into the space about the tank to aheight substantially less than the height of the tank, liquid levelsensing means for determining the presence of cold liquid within saidcold liquid receiving means, and means responsive to theliquid levelsensing means for withdrawing liquid from the cold liquid receivingmeans.

3. A leak protecting system for the storage and transportation ofextremely cold liquids in containers of the type having at least onestorage tank located within a thermally insulated space with there beingan expansion space between the sides of the storage tank and the sidesof the thermally insulated space comprising a cup-shaped cold liquidreceiving container positioned at the bottom of the storage tank, theside walls of said container being positioned intermediate the sides ofthe storage tank and the sides of the thermally insulated space andextending upwardly to a height substantially less than the height of thetank, liquid level sensing means for determining the presence of liquidwithin said cold liquid receiving means, and recirculating pump meansfor withdrawing liquid from the cold liquid receiving means in responseto the liquid level sensing means and returning it to the storage tank.

4. A liquid protection system in the storage and transportation ofextremely cold liquids having a boiling point so low as to dangerouslyembrittle and weaken ordinary steel plate, comprising a self-supportingtank for such liquid having top and bottom walls and side walls, athermally insulated container completely surrounding said tank andinsulating its contents to provide a safe temperature at he outsidesurface of said insulated container, there being a space between theside walls of the tank and the adjacent walls of the insulatedcontainer, a liquid-impervious barrier in said space, the upper part ofsaid barrier extending upward only a fractional part of the way from thebottom of said space and defining together with the outer wall of saidtank a trap for collecting any liquid dripping down the outer side ofsaid tank without permitting said liquid to reach the insulatedcontainer, and means for removing liquid from said trap to prevent thebuilding up of substantial hydrostatic pressure against the inner wallsof said trap, there being also a space between the bottom wall of thetank and the adjacent bottom wall of the insulated container,

the bottom part of said barrier being substantially horizontal andunderlying the bottom wall of said tank and being spaced therefrom todefine, together with said upwardly-extending' part of the barrier, aliquid-impermeable drip pan.

References Cited in the file of this patent

4. A LIQUID PROTECTION SYSTEM IN THE STORAGE AND TRANSPORTATION OFEXTREMELY COLD LIQUIDS HAVING A BOILING POINT SO LOW AS TO DANGEROUSLYEMBRITTLE AND WEAKEN ORDINARY STEEL PLATE, COMPRISING A SELF-SUPPORTINGTANK FOR SUCH LIQUID HAVING TOP AND BOTTOM WALLS AND SIDE WALLS, ATHERMALLY INSULATED CONTAINER COMPLETELY SURROUNDING SAID TANK ANDINSULATING ITS CONTENTS TO PROVIDE A SAFE TEMPERATURE AT THE OUTSIDESURFACE OF SAID INSULATED CONTAINER, THERE BEING A SPACE BETWEEN THESIDE WALLS OF THE TANK AND THE ADJACENT WALLS OF THE INSULATEDCONTAINER, A LIQUID-IMPERVIOUS BARRIER IN SAID SPACE, THE UPPER PART OFSAID BARRIER EXTENDING UPWARD ONLY A FRACTIONAL PART OF THE WAY FROM THEBOTTOM OF SAID SPACE AND DEFINING TOGETHER WITH THE OUTER WALL OF SAIDTANK A TRAP FOR COLLECTING ANY LIQUID DRIPPING DOWN THE OUTER SIDE OFSAID TANK WITHOUT PERMITTING SAID LIQUID TO REACH THE INSULATEDCONTAINER, AND MEANS FOR REMOVING LIQUID FROM SAID TRAP TO PREVENT THEBUILDING UP OF SUBSTANTIAL HYDROSTATIC PRESSURE AGAINST THE INNER WALLSOF SAID TRAP, THERE BE-